(1) Field of the Invention
This invention relates to a coating composition for metals, more particularly to a coating composition having excellent properties in fabricating properties, corrosion resistance, etc. and containing a specified, modified epoxy resin and a phenol resin and/or an amino resin.
(2) Description of the Prior Art
A so-called precoat metal plate, which is prepared by coating a coating composition onto a metal plate as a substrate material directly or after subjecting the metal plate to a pretreatment or a chemical treatment followed by curing, has been widely used in practice in the art. The precoat metal plate is properly shaped and processed to be employed for various uses as a coated and fabricated metal product. However, the aforementioned precoat metal plate raises such problems that a coated film of such a fabricated metal product has a certain limit on fabricating properties particularly those in bending and shaping, so that a severe deformation of the fabricated metal product on fabrication causes the coated film crazing and peeling.
In order to solve the aforementioned problems, there have been made in the art various proposals such as a process in which a coating composition containing a polymer resin capable of improving fabricating properties is coated on a metal plate as a substrate material, development of a coating composition capable of providing a coated film with plasticity without causing deterioration in film performances, etc.
As a matter of fact, the process according to the first proposal as above has such drawbacks that a binder for use in the coating composition is hardly dissolved in a solvent because of high molecular weight, and that increase in the rotational speed on roll coating performance results in unevenness in coating, for example, stringing and flashing, and is difficult to be put practical use.
On the other hand, the coating composition according to the second proposal as above raises such problems that a plasticizing component is liable to remain in a cured film, and particularly that on the application of the coating composition to an inner surface of vessels for use in food and drink, the plasticizing component migrates into food to be undesirable from the standpoint of food sanitation.